Folkert van Heusden <[EMAIL PROTECTED]> wrote: > > > > What about a zero-copy read-interface? > > > An ioctl (or something) which enables the kernel to do dma directly to > > > the userspace. Of course this should be limited to the root-user or a > > > user with special capabilities (rights) since if a drive screws up, data > > > from a different sector (or so) might end up in the proces' memory. Of > > > course copying a sector from kernel- to userspace can be done pretty > > > fast but i.m.h.o. all possible speedimprovements should be made unless > > > unclean. > > Just use mmap(). Unlike your proposal, it cooperates with the page > > cache. > > Doesn't that one also use copying? I've also heard that using mmap is > expensive due to pagefaulting. I've found, for example, that copying a > 1.3GB file using read/write instead of mmap & memcpy is seconds faster. >
You can use remap_file_pages() to read all the pages into pagecache and then instantiate all their pte's in a single syscall. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/